Gibson's first-generation Robot Guitar, in blue sunburst, was limited to 4000 units (sold out). This month [April 2008] Gibson released two new models of a second-generation limited edition of 1000 units in purple metallic (sold out). This week Gibson will announced the release of another 1000 units total of the second-generation models in metallic green, including an SG model (middle bottom), which was introduced in 1961 as a new lighter weight "solid guitar"--SG--unlike the original Les Paul which has a chambered body. The SG has a double-cutaway and a neck with a more slender profile compared with the classic round-neck of the original Les Paul, which was designed in the 1950s and was used as the inspiration for both the first-generation Robot Guitar and the second-generation Robot Les Paul Studio Ltd. (middle top). Also new for the second-generation robot guitars is a locking input jack from Neutrik AG (Liechtenstein, Germany). The locking 1/4-inch jack (upper left and lower right) provides a secure input that prevents accidental disconnection.